The multiplicity of an association represents how many rows there are in
one view for each row of the other.

For example, let us say that you create an association between the view
customer and the view order, the multiplicity at the endpoint
customer (role name orders) is 1 and at the endpoint
order (role name customer) is *. This indicates that for
each row of the customer view there are zero, one or more rows in
the order table; and for each row in the order view there is one
and only one row in the view customer.